I've been trying to find a source for it for a while. Many other types of Camellia seem to do quite well here in North Florida among other parts, so I see no reason why sinensis wouldn't do just fine. You can get seeds on eBay for very little money. There's someone making a fortune selling little seedlings of the plant, of which I'm sure they started from seed, so there's hope that it's certainly achievable for cheap :)

Interesting fact about green tea versus black. The green tea leaves are first steamed to destroy enzymes in the leaves, so that they stay green rather than ferment and turn brown or black. It's just like blanching green beans before freezing. I guess you can just add boiling water to the fresh leaves, but this is not the same as traditional green tea which is steamed and then dried under controlled conditions.

The enzymes in the tea leaves promote oxidation of the leaves after they are picked from the tea plant. Just as dying tree leaves turn from green to gold, red and brown in the Fall, so wilting tea leaves start to go brown and black under warm humid conditions. This is a form of natural oxidative decay, a bit like apple flesh turning brown after it is cut. Therefore the enzymes have to be knocked out by steam in order to stop this "fermentation" and retain the green color of the leaves as they are dried. This is also done to things like green beans by blanching before freezing...otherwise the enzymes can cause the beans to turn black and leathery.
This fermentation is allowed to occur naturally when black tea is made, because the leaves are not steamed and the enzymes are intact. The fermentation process increases the body, astringency and complexity of the flavor but also removes some of the anti-oxidant components of the tea.

In Fall 2011 my husband and I went to Charleston, SC. One of the things we did there was to go out to the Charleston Tea Plantation. It's the only tea plantation in the country. The tour was great! At the processing plant they went into great detail on how tea is dried and the processes it goes through to create the final product. Very interesting and a lot more complicated than I ever thought. Can you do this at home? Not really sure but you might google the process.